Speaking to about a thousand supporters of the organization, which is a leading sexual and reproductive health care advocate and provider for women, Mr. Obama described himself as “a president who’s going to be right there with you, fighting every step of the way.”

He lauded the organization’s work in providing cancer screening and contraceptive health care, and criticized attempts by conservatives to use the organization as “a punching bag.”

“After decades of progress, there's still those who want to turn back the clock to policies more suited to the 1950s than the 21st century. And they've been involved in an orchestrated and historic effort to roll back basic rights when it comes to women's health,” he said.

Obama’s appearance coincided with a wave of state legislation aimed to restrict access to abortion, according to the Guttmacher Institute, a non-profit think tank in Washington that researches and tracks policy involving sexual and reproductive health.

The organization says that in the first three months of 2013, state legislators in 42 states introduced 694 provisions related to reproductive health and rights, 93 of which have been approved by at least one legislative body. About half, or 47 percent, of the measures seek to restrict full access to abortion.

Legislators in 10 states have introduced proposals to ban all, or nearly all, abortions while 10 other states have passed, or are positioned to pass, legislation to ban abortions after 20 weeks of pregnancy.

Obama criticized some of the measures, particularly a North Dakota law passed in March that bans abortions as early as six weeks, or when a fetal heartbeat is detected.

“A woman may not even know that she’s pregnant at six weeks,” Obama said regarding the law, which is the most restrictive in the nation to date.

Some conservative organizations blasted the president’s speech, linking Planned Parenthood to the trial of Kermit Gosnell, a West Philadelphia abortion provider charged with killing four newborns during abortions, as well as the overdose death of an adult patient. They say the organization should be held accountable for failing to report Mr. Gosnell’s actions.

“It is outrageous that President Obama addressed the Planned Parenthood gathering this morning at a time when Planned Parenthood has been exposed for having known about the Gosnell horrors, yet took no action to report this abuse of women and babies,” Maureen Ferguson, a senior policy adviser for the Catholic Association, an advocacy group in Washington, told the Washington Post Friday.

Likewise, in a statement released Friday, Marjorie Dannenfelser, president of the Susan B. Anthony List, an advocacy group in Washington, said that Planned Parenthood “chose not to act to help end the killing of newborn babies and butchering of women…. It seems that nothing, not even eyewitness accounts of Gosnell-style conditions in their own clinics, is enough to make President Obama reconsider his unyielding support for Planned Parenthood.”

Obama did not mention the trial during his Friday remarks.

The jury in the Gosnell case is expected to hear closing arguments Monday. Planned Parenthood spokesman Eric Ferrero told the Washington Post Friday that the organization denounced Gosnell’s actions and called the trial “a horrifying and outrageous case.”

“Gosnell ran a criminal enterprise, not a health care facility, and [for] that he should be punished to the fullest extent of the law,” Mr. Ferrero said.